Impact of comorbidities on the performance of interferon-gamma release assay in an elderly Greek population without overt immunodeficiency.

Background The prevalence of latent tuberculosis infection (LTBI) increases with age. Interferon-gamma release assay (IGRA) is a T-cell based assay widely used for the detection of LTBI. Objectives To identify the prevalence of LTBI among an elderly Greek population using IGRA and to evaluate comorbidities associated with LTBI. Methods Individuals aged at least 65 years who were non-immunocompromised and had no history of active tuberculosis infection (TBI) underwent IGRA to identify LTBI. Participant characteristics were compared between the LTBI and non-LTBI groups. Interferon-gamma (INFγ) levels were analysed in each group. Results A total of 130 (38.7%) participants with LTBI and 206 (61.3%) participants without LTBI were included. Multivariate logistic regression analysis identified the following features that were independently associated with a positive IGRA result: female sex (odds ratio [OR]: 0.45; 95% confidence interval [CI]: 0.28-0.72; P=0.001), chronic heart failure (OR: 0.41; 95% CI: 0.22-0.77; P=0.005), history of major surgery (OR: 0.55; 95% CI: 0.33-0.92; P=0.022) and Charlson Comorbidity Index >3 (OR: 3.06; 95% CI: 1.46-6.40; P=0.003). Production of stimulated INFγ was significantly lower in the non-LTBI group. Conclusions Female sex, history of chronic heart failure and history of any surgical intervention were independently associated with a negative IGRA result, and CCI >3 was associated with a positive IGRA result. These results indicate careful interpretation of IGRA is required among elderly individuals with these characteristics.